Climate Update 39 - September 2002

28 March 2007 - 11:15am

Science Centres: Climate

September

Climate

River flows

Soil moisture

Three-month outlook

Checkpoint

Backgrounder

Backgrounder
Backgrounder 2002 rainfall to date Large areas of New Zealand have received near normal rainfall. Parts of Waikato, Bay of Plenty, and the northeast and southwest of the South Island have been drier than average. Total rainfalls for 1 January to 31 August 2002. Update on the SOI The mean Southern Oscillation Index (SOI) for August was -1.8, with the three month average now at -1.1. The present moderate El Niño is expected to be weaker than the 1997-98 event. Further general information on El Niño is available on the World Meteorological Organization web site.

Checkpoint
Outlook and outcome – June to August 2002 Rainfall was generally as expected over the South Island as well as the central North Island, but wetter than forecast in the east and parts of the north of the North Island. Air temperatures were normal or above normal, as was predicted, for all districts except the east of the North Island, where normal temperatures were predicted but the winter temperature outcome was above normal. River flows were normal in Waikato, Nelson, and coastal Otago and Southland, and below normal in Marlborough and Canterbury, as they were predicted to be.

Climate
New Zealand Climate Mild conditions widespread Despite a cold, wintry outburst during the last week, August was warmer than usual, especially in the South Island.

Three-month outlook
The outlook for September to November 2002 An El Niño event is under way in the tropical Pacific, but is likely to be much weaker than the 1997-98 episode.

River flows
New Zealand River Flows August streamflows varied August flows were below normal for most of the country, but above normal around Gisborne and Hawke’s Bay, and in parts of inland Otago and the South Island hydro lakes.

September
Climate Update is a summary each month of New Zealand's climate, including soil moisture and river flows. September 2002 – Number 39 August’s climate: It was drier than normal in Marlborough, mid Canterbury, and Bay of Plenty for the second consecutive month. August’s river flows: August streamflows varied. Soil moisture levels: Pockets of drier than normal soils were evident at the end of August. Three month outlook: Warmer than normal in the North Island and north of the South. Checkpoint: How well are we doing with our predictions? Backgrounder: Estimating changing fre

Soil moisture
Soil moisture on 31 August Pockets of drier than normal soils were evident at the end of August in Bay of Plenty, Hawke’s Bay, Marlborough, Canterbury, and in inland and coastal Otago. Rainfall was below average for both July and August in northern and central areas of the South Island, resulting in lower than normal subsoil moisture content in Marlborough and mid and south Canterbury. Soil moisture deficit in the pasture root zone at the end of August (right) compared with the deficit at the same time last year (centre) and the long term end of August average (left).